1. Field of the Invention
The present invention relates to umbrellas and more particularly to an auto-opening umbrella in which the operation is smooth when the umbrella is opened and folded and the umbrella can be stored more compactly when it is folded.
2. Description of Related Art
Auto-opening umbrellas are well known. One type of such umbrella is disclosed in U.S. Pat. No. 6,158,452 as shown in FIGS. 6 and 7. It is characterized by the provision of a main shaft A, a bottom running hub D, an intermediate running hub D1, a spiral spring F disposed between the running hubs D and D1, a radiating frame of ribs M (only one is shown), a frame of supporting ribs S (only one is shown), and a frame of linkage beams E (only one is shown). It is known that the auto-opening force is provided by the compressed spring F. Hence, the spring F, the supporting ribs S, and the second pivotal coupling devices P are critical to the operation of the auto-opening umbrella. In the identified patent, the second pivotal coupling devices P are formed by plastic injection molding. A coupling hole H is extended parallel to the second pivotal coupling device P. An upper end E1 of linkage beam E is shaped like a hook. Also, an arcuate trace is formed as the upper hook E1 is pivoted in the coupling hole H in opening the umbrella. However, such pivoting operation is not smooth when the spring F is expanded. This is because a diameter of the coupling hole H is only slightly larger than that of the upper end E1, i.e., very small allowance. Moreover, an assembly of the umbrella is time consuming, resulting in an increase in the manufacturing cost.
Another auto-opening umbrella formed of FRP (Fiber Reinforced Plastics) is shown in FIG. 8 in which a linking block T is extended a distance from the second pivotal coupling device P on the supporting rib S and perpendicular thereto for effecting a pivot relative to an FRP linkage beam C. Thus, the linkage beam C can be pivotal about the second pivotal coupling device P and the bottom running hub D by pivotably connecting upper and lower joint C1 and C2 to the linking block T and the bottom running hub D respectively. However, such construction makes the FRP umbrella frame unacceptable large after folded since the ribs M are spaced apart from the second pivotal coupling devices P by a distance substantially as the width of the linking block T. As such, the umbrella is disadvantageous in consideration of storage, packing, and transportation.
Thus, it is desirable to provide an improved auto-opening umbrella in order to overcome the above drawbacks of prior art.
It is an object of the present invention to provide an enhanced frame of an auto-opening umbrella which is more compact after being folded.
It is another object of the present invention to provide an enhanced frame of an auto-opening umbrella which is very smooth in an folding and opening operation.
To achieve the above and other objects, the present invention provides a frame of an auto-opening umbrella comprising a shank including a slidable lower ring, a slidable intermediate ring both thereon, a stationary upper hub, and an elastic means biased between the intermediate and the lower rings; a rib assembly including a plurality of ribs; a spreader assembly including a plurality of spreaders, each of them being pivotably coupled to each of both the ribs and the intermediate ring; a plurality of links having an inner hooked end and an outer hooked end wherein each of the inner hooked ends is pivotably coupled to the lower ring; and a plurality of substantially hollow cylindrical intermediate joints each including a central through hole with the spreader passed through and fastened therein, two spaced downward extending bottom lugs, a bar being across the lugs; wherein the outer hooked end of each link is pivotably coupled to the bar. In one aspect of the present invention, the bar is disposed at a position less than half of a projected distance of the lug relative to a bottom of the intermediate joint.
In another aspect of the present invention, the link is made of stainless steel.
In still another aspect of the present invention, the outer hooked end of each link is disposed around more than half of a circumference of the bar.
In a further aspect of the present invention, the recess is in communication with the central through hole and the outer hooked end of each link is sufficiently smaller than the recess so that the ribs are spaced apart from the spreaders by a substantially zero distance when the umbrella is folded.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with